The objective of this project is to develop a better understanding of the role of chemical mediators in human bronchial anaphylaxis. This goal will be approached through in vitro studies of excised human bronchial tissue supplemented by analogous studies of guinea pig trachea. Two experimental models will be employed. These are (a) organ bath studies in which sensitized airway tissue is challenged with antigen, and smooth muscle contraction and chemical mediator release are measured, and (b) organ culture studies of the anaphylactic release of lipoxygenase products of radiolabeled arachidonic acid (AA). The organ bath studies will focus on the role of leukotrienes (LTs) and other endogenous chemicals in mediating the response of sensitized airway tissue to antigen. We will measure airway smooth muscle contraction, quantify the release of histamine and LTs, examine the effect of inhibitors of LT synthesis and anti-LT antibodies on allergic bronchospasm, and evaluate the effect of synthetic LTC4 and LTD4 on human bronchial smooth muscle. We will study the effect of beta-adrenergic and histamine H2 agents, various prostaglandins, adenosine LTC4 and LTD4 on anaphylactic mediator release from human bronchus. The organ culture experiments will be directed toward developing a profile of lipoxygenase products released during anaphylaxis and understanding the role of AA metabolism through the lipoxygenase pathways in the regulation of airway mast cell and smooth muscle cell function. These studies should further elucidate the role of endogenous chemicals in tissue and cellular processes central to the pathogenesis of bronchial asthma and provide insights necessary for the development of novel and specific procedures for interrupting the disease process.